The present invention is directed to articles of footwear, and in particularly, to footwear having relatively stiff upper shells mounted to a sole. Accordingly, the present invention has specific application in the ski and hiking boot industries.
The technology developed in the skiing industry in recent times has been quite fast paced, with improvements being made to skis, bindings and the boots. One area of interest has been the interrelationship between alpine, or "downhill", skiing and nordic, or "cross-country", sking. In alpine skiing, a rigid ski boot is locked into front and rear bindings on a relatively wide ski that is provided with cutting edges for permitting fast turns on steep downgrades. In alpine skiing, a typical ski boot has a completely rigid sole and a compeltely rigid upper shell that extends over the foot, around the ankle and over a portion of the lower leg. Such ski boots do not typically have the ability to flex so that the entire lower leg and foot of the human body is maintained in a relative unalterable configuration. Some ski boots, such as the boot shown in U.S. Pat. No. 4,461,103 issued July 24, 1984 to Annovi, provide a pivot between the foot shell and the ankle shell to allow limited relative movement. These boots often utilize resilient stiffening members so that resilient force may be applied by the skier to the toe portion of the foot by bending the knees forward against the resilient member.
On the other hand, in nordic skiing, it is important that a wide range of flexibility be maintained between the rear of the foot and the toe of the foot since nordic skiing has similarities to walking. In the past, typical nordic skiing boots or shoes have comprised a rather pliable leather article of footwear having a forward toe hinge that mounts in a front binding of a relatively narrow ski. The rear of the nordic boot is not secured to the ski so that the user may bend the boot along an area adjacent the ball of the foot. Indeed, for competent nordic skiing, it is necessary that the pivotal relationship between the toe and the heel of the foot exceed the typical range of flexing movement that takes place during walking.
One problem with nordic boots, however, has been their inability to resist torsional rotation about a longitudinal axis and their inability to resist lateral motion of the heel. This problem was recognized in U.S. Pat. No. 4,505,056 issued Mar. 19, 1985 to Beneteau. In the Beneteau patent, a cross-country ski boot is provided having a plurality of weakening ribs that extend adjacent the ball of the foot across the sides and top of thereof. To allow the boot to pivot, Beneteau encases his boot in a relatively stiff shell having a front toe portion and a rear heel portion separated and interconnected by a flat, flexing region of the rigid shell. The shell is then pivotally attached to a ski binding so as to prevent torsional rotation and lateral movement of the heel.
In addition to the prior art devices noted above, many other inventors have recognized the lack of comfort generated by an inflexible alpine boot when the skier removes the skis and attempts to walk from one location to another. To this end, there have been numerous developments of ski boots which flex slightly to allow greater ease in walking. One such prior art device is shown in U.S. Pat. No. 3,972,134 to Kastinger wherein a boot having a stiff sole and a rigid upper shell includes regions of reduced strength at a fore part of the foot to allow bending of the foot forwardly of the ankle, and pleats are provided at a forward part of the ankle to facilitate walking. U.S. Pat. No. 3,535,800, issued Oct. 27, 1970 to Stohr, shows a ski boot that flexes about a pivot on the ankle with this flexing accomplished by baffles extending forwardly and rearwardly of the boot at the ankle region. U.S. Pat. No. 3,953,930, issued May 4, 1976 to Ramer, also discloses a ski boot designed for greater ease in walking. In the Ramer structure, a flexible sole is provided to support a rigid shell defining a heel portion and a forward foot portion being telescopically inserted into a rigid shell defining a toe portion for the boot. As the skier walks in this boot, the toe portion and the heel/foot portion telescope with respect to one another. Limit stop means for preventing hyperextension of the floating toe portion is provided to limit relative movement between the toe portion and the heel portion.
Despite the improvements of these prior art patents over earlier ski and hiking boots, there remains the need for a boot that may be employed for both alpine skiing and for nordic skiing, which boot allows pivotal or rotational movement about the ball of the foot while at the same time remaining rigid against torsional rotation and lateral movement of the heel when the toe portion is secured to a front ski binding. There is further a need that allows greater flexibility of pivotal movement between the toe portion and heel portion so that nordic style skiers may implement telemark turns on relatively steep downgrades. There is further a need to provide a boot that can be used for nordic skiing, alpine skiing and for walking, which boot is acceptable in a wide variety of typical bindings.